1. Field of the Invention
The present invention relates to a reinforcement structure for a rear wheel of a vehicle, and more particularly to a reinforcement structure for a rear wheel of a vehicle adapted to reinforce a strength to a rear wheel housing unit of a vehicle body to thereby reduce generation of noise caused by changes of a sound field inside a vehicle.
2. Description of the Prior Art
Generally, a vehicle body receives a load input from a road surface via a suspension system while a vehicle is running, to cause a frame of the vehicle body to be deformed. The deformation of the frame serves to change air flow, resulting in changes in a sound field inside the vehicle. The change of the sound field in turn results in noise, so called, road noise.
In order to reduce the road noise, an increase of strength to a chassis mounting unit such as a suspension, sub-frame, rear cross member and the like is much required.
Meanwhile, a rear body of a conventional vehicle is formed with a rear wheel housing 12 protruded to an upper side of an inner area of the vehicle for installing a shock absorber of a rear suspension system, wheels and the like toward left/right sides of rear floor panel 10 (see FIG. 1).
The rear wheel housing 12 includes a wheel housing cover 14 for securing an upper end of a shock absorber to an upper end thereof, a wheel housing inner panel 16 semi-spherically extended downward from the wheel housing cover 14, a flange coupling unit 18 extended to an external side of the wheel housing inner panel 16, a cover reinforcing material 20 encompassing a marginal part of the wheel housing cover 14 and a quarter inner panel 30 coupled to the flange coupling unit 18 (see FIG. 2).
However, as a result of normal mode analysis through Computer Aided Engineering CAE against the wheel housing cover 14 and wheel housing inner panel 16 of a conventional rear wheel housing 12, it was found out that the vibration level of the wheel housing inner panel 16 is increased at an intermediate speed of booming domain which is between 200 Hz and 400 Hz ("A" domain in FIG. 2). Furthermore, it was also found out that vibration level of the wheel housing cover 14 is increased at a high speed booming domain of 400 Hz.about.600 Hz.
When the wheel housing cover 14 and the wheel housing inner panel 16 at the rear wheel housing 12 are increased in vibration levels thereof at respectively intermediate and high speed booming domains, there occurs a problem of noise generation due to resonance with frequency resulted from the load input from the external side.
Under the presumption that reinforced strength to the mounting part of the wheel housing cover 14 at the rear wheel housing 12 decreases the vibration level generated when the load of external force input from the road surface to thereby reduce the level of noise generation, an analysis was made through a frequency response function curve in FIG. 3 which classifies vibration level versus strength level against three mounting parts formed at the wheel housing cover 14 at the rear wheel housing 12 for respective domains of low, intermediate and high frequencies.
As a result, in comparison with a third mounting part 14c formed at an inner side of the wheel housing cover 14 of the rear wheel cover 12, it was found out that sensitive inertance exists at intermediate and high booming domains of first and second mounting parts 14a and 14b formed forward and backward directions of vehicle body at external side of the wheel housing cover 14.
At this point, the vibration level is based on vertical direction (Z axis) of the vehicle body while change of accelerated speed (m/s.sup.2) per external unit power is defined in log scale. Furthermore the strength level represents stiffness level (Kgf) required for moving a unit field (mm) while frequency domain defines engine revolutions from 0 Hz to 800 Hz.
The frequency domain whose peak of vibration level abruptly rises can be interpreted that resonance in alignment with the load input from external side is high according to the frequency response function curve illustrated in FIG. 3. The fear of high resonance may be justly inferred to be a generation cause of road noise according to sound field change inside the vehicle.
According to the analysis, a requirement is that a structure strength reinforcement to the first and second mounting parts 14a and 14b at the wheel housing cover 14 and to the wheel housing inner panel 16 at the rear wheel housing 12 should do something in relieving sensitive inertance caused by a sudden rise of frequency due to resonance with the load input from the road surface while a vehicle is running.
The present invention is disclosed to solve the aforementioned problems and it is an object of the present invention to provide a reinforcement structure for a rear wheel housing of a vehicle constructed to reinforce a structural stiffness against a wheel housing inner panel and a wheel housing cover at the rear wheel housing to reduce inertance against the rear wheel housing part at intermediate and high booming domains, thereby reducing road noise inside the vehicle caused by sound field change according to the resonance.
In accordance with the object of the present invention, there is provided a reinforcement structure for a rear wheel housing of a vehicle, the rear wheel housing including a wheel housing cover and a wheel housing inner panel protruded upwards to install a shock absorber of a rear suspension system and wheels to left/right tip end parts of a rear floor panel, the structure comprising:
first and second reinforcement members for being respectively coupled up and down at a front corner part formed by front and side surfaces of the wheel housing inner panel and extended to define closed sections upto a rear floor panel; PA1 a third reinforcement member extended fieldwise and coupled to a bottom surface of the wheel housing cover between first and second mounting parts formed toward an external side of the vehicle body; and PA1 a fourth reinforcement member crosswise extended and coupled to a central portion of the first and second mounting parts.